Apparatus and Method for the Detection and Treatment of Atrial Fibrillation

ABSTRACT

Embodiments of the invention provide methods for the detection and treatment of atrial fibrillation (AF) and related conditions. One embodiment provides a method comprising measuring electrical activity of the heart using electrodes arranged on the heart surface to define an area for detecting aberrant electrical activity (AEA) and then using the measured electrical activity (MEA) to detect foci of AEA causing AF. A pacing signal may then be sent to the foci to prevent AF onset. Atrial wall motion characteristics (WMC) may be sensed using an accelerometer placed on the heart and used with MEA to detect AF. The WMC may be used to monitor effectiveness of the pacing signal in preventing AF and/or returning the heart to normal sinus rhythm (NSR). Also, upon AF detection, a cardioversion signal may be sent to the atria using the electrodes to depolorize an atrial area causing AF and return the heart to NSR.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/757,865, filed Apr. 9, 2010, entitled “Apparatus and Method for theDetection and Treatment of Atrial Fibrillation” which is a continuationof U.S. patent application Ser. No. 12/427,733, filed Apr. 21, 2009,entitled “Apparatus and Method for the Detection and Treatment of AtrialFibrillation”, now U.S. Pat. No. 8,644,927, issuing on Feb. 4, 2014. Theaforementioned priority applications being hereby incorporated byreference in their entirety for all purposes.

FIELD OF THE INVENTION

Embodiments described herein relate to an apparatus and method fordetection and treatment of atrial fibrillation. More specifically,embodiments described herein relate to an apparatus and method fordetection and treatment of atrial fibrillation using distributed bipolarelectrodes placed on the surface of the heart to detect the earliestonset of fibrillation.

BACKGROUND

The heart has four chambers, the right and left atria and the right andleft ventricles. The atria serve as primer pumps to the ventricles whichin turn pump blood to the lungs (the right ventricle) or the aorta andthe remainder of the body (the left ventricle). The heart is essentiallyand electromechanical pump, which contracts and pumps blood by means ofa wave of depolarization that spreads from the atria to the ventriclesin a timed fashion through a series of conduction pathways. Cardiacarrhythmia is a condition afflicting the heart and is characterized byabnormal conduction patterns which in turn can affect the pumpingefficiency in one of more chambers of the heart. It can occur in eitherthe atria, ventricles or both. Particular types of Atrial arrhythmia cancause a condition known as atria fibrillation (AF) in which the pumpingefficiency of the atria are compromised. Instead of contracting in acoordinated fashion, the left or right atria flutter with little or nopumping efficiency.

During an episode of AF, the normal electrical impulses that aregenerated by the sin θ-atrial node (the SA node), the natural pacemakerof the heart are overwhelmed by disorganized electrical impulses, knownas ectopic foci that may originate in the atria or pulmonary veins,leading to conduction of irregular impulses to the atria and theventricles. This can result in an irregular heartbeat, known as anarrhythmia which may occur in episodes lasting from minutes to weeks, oryears. Left unchecked, AF often progresses to become a chroniccondition.

Atrial fibrillation is often asymptomatic, and while not immediatelylife-threatening, may result in palpitations, fainting, chest pain(angina), or congestive heart failure. Patients with AF have asignificantly increased risk of stroke and pulmonary embolism due to thetendency of blood to pool and form clots or emboli in the poorlycontracting atria which are then sent to the lungs in the case of theright atria causing pulmonary embolism, or the brain causing stroke.

Atrial fibrillation may be treated with medications, implantedventricular defibrillators or surgical procedures. The currentmedications used either slow the heart rate or revert the heart rhythmback to normal. However patients must remain on medication for life andmany patients cannot be successfully treated with medication. Implantedventricular defibrillators may be used to deliver a series of highvoltage electric shocks to convert AF to a normal heart rhythm in atechnique known as synchronized electrical cardioversion. However, theseshocks are extremely painful and may cause the patient to pass orliterally be knocked to the ground from the shock. Surgical andcatheter-based therapies may also be used to ablate or destroy portionsof the atria and pulmonary veins containing the ectopic and other fociresponsible for the generation of arrhythmias causing AF; however theserequire open heart surgery, cardiac catheterization or both and have metwith limited success. Thus, there is a need for improved methods anddevices for the treatment of atrial fibrillation.

BRIEF DESCRIPTION

Embodiments of the invention provide apparatus, systems and methods forthe detection and treatment of atrial fibrillation and relatedconditions. Many embodiments provide a system including a pacemakercoupled to endocardial and/or epicardial leads having a distributedpattern of bipolar electrodes for the early detection and treatment ofatrial fibrillation.

In a first aspect, the invention provides an endocardial lead havingmultiple bipolar electrodes that attach to the endocardial surface ofthe right atria in a distributed pattern for the early detection andtreatment of fibrillation in the right atria. Preferably, the electrodesare arranged in a circular or other pattern on the endocardial surfaceof the right atria to define an area for detecting the location of afoci of aberrant electrical activity causing onset (including earlieronset) of atrial fibrillation. In specific embodiments, the foci can bedetected by an algorithm in the pacemaker which identifies the locationon the endocardial surface (by the nearest electrode pair) having theearliest activation (i.e., depolarization) during an episode of AF.

Once a foci is detected, the electrodes nearest the foci can then beused to send a pacing signal at that site to prevent the site fromcausing atrial fibrillation. In some embodiments, that site of earlyactivation can be paced continuously. The lead is coupled to a pacemakerto send sensed signals from each electrode pair back to the pacemakerelectronics for analysis to determine the onset of atrial fibrillationor a signal predictive or the onset of atrial fibrillation. The lead canbe positioned by in the right atria by introduction and advancement fromthe jugular vein using cardiac catheterization techniques known in theart.

In particular embodiments, the electrodes can be positioned in acircular, oval or related pattern around the SA node. The electrodepairs can be positioned on a circular or oval shaped patch that isattached to the endocardial surface using mechanical attachment elementsuch as a helical screw, barbed needle or other attachment means such asa biocornpatible adhesive. The adhesive can comprise a thermallyactivated adhesive that is activated by heat from the body or resistiveheating from signals sent to the electrode pair. The patch can comprisea PTFE, polyester or other biocornpatible material known in the art andis desirably configured to bend and flex with the motion of the heartwall. It may also include one or more nonthrombogenic coatings includingcoatings impregnated with various elutable drugs known in the art suchas TAXOL to prevent thrombus, platelet and other cell adhesion. Theelectrodes can comprise a radio-opaque or echogenic material forvisualizing a location of the electrodes in the heart under flouroscopy,ultrasound or other medical imaging modality. Also the patch can includea section made out of such materials to serves as a marker forvisualizing the location of the electrodes in the heart.

In a related aspect, the invention provides an epicardial lead havingmultiple bipolar electrodes that attach to the epicardial surface of theleft atria in a distributed pattern for the early detection andtreatment of fibrillation in the left atria. Preferably, the electrodesare arranged in a pattern on the epicardial surface of the left atria toelectrically map the atria so as detect the location of a foci ofaberrant electrical activity causing early onset of atrial fibrillationin the left atria. The pattern includes placement of one or moreelectrodes adjacent one or more of the pulmonary veins so as to detectfoci in these locations. Additionally, in left atria lead embodiments,the lead can also be coupled to a 3-axis accelerometer placed on theepicardial wall of the atria to sense atrial wall motion predictive ofatrial fibrillation and normal sinus rhythm. The signal from theaccelerometer may be used as a sole indication of AF, or it may be usedto supplement the electrical signals from the bipolar leads positionedon the left atria to increase the predictive power of various algorithmsused by the pacemaker for the detection of AF. Additionally, sensoryinputs from the accelerometer can also be used to assess theeffectiveness of atrial pacing signal in preventing AF and/or returningthe heart to normal sinus rhythm.

In another aspect, the invention provides an apparatus, system andmethod for performing low voltage distributed cardioversion forconverting the atria from a fibrillative state back to normal sinusrhythm. In these and related embodiments, the pacemaker cansimultaneously send a higher voltage pacing signal (in the range of 8 to10 volts) to all pairs of electrodes (e.g., on the particular atriallead) to stimulate a large enough area of the atria to eliminate thearrhythmia. By using voltages lower than those typically used duringexternal or internal cardioversion (which can be in the hundreds ofvolts for internal conversion to the thousands for external conversion)the pain experienced by the patient can be greatly reduced. The otherbenefit of this approach is that by using bipolar electrodes at eachsite, the electrical energy delivered to the heart can be contained in avery small region so that the risk of stimulating the ventricles (anunwanted effect in this case) is very small.

Further details of these and other embodiments and aspects of theinvention are described more fully below, with reference to the attacheddrawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral view showing an embodiment of a system for thetreatment of atrial fibrillation including a pacemaker and various leadsgoing to the atria and ventricles for AF detection and pacing andventricular pacing.

FIG. 2 is a cross sectional view of the heart showing the placement inthe heart of the various leads from the embodiment of FIG. 1

FIG. 3 is a side view of the right atria showing an embodiment of anatrial lead having a distributed pattern of bipolar electrodes placed onthe endocardial surface of the right atria for the detection andtreatment of AF.

FIG. 4 is a side view of the left atria showing an embodiment of aparallel atrial lead configuration connected to a distributed pattern ofbipolar electrodes placed on the epicardial surface of the left atriafor the detection and treatment of AF.

FIG. 5 is a cross sectional view showing an embodiment of an atrial leadfor sensing and pacing.

FIG. 6 a is a top down view showing an embodiment of a bipolar electrodeassembly including a pair of bipolar electrodes positioned on a patch orother support layer.

FIG. 6 b is a cross sectional view showing positioning of an embodimentof the bipolar electrode assembly on the endocardial wall.

FIG. 7 is a block diagram illustrating some of the typical circuitry ona pacemaker or other implantable pacing or stimulating device.

FIGS. 8 a-8 c are graphs showing an EKG for normal sinus rhythm (FIG. 8a) and during an episode of atrial fibrillation, including theventricles (FIG. 8 b) and atria (FIG. 8 c).

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide apparatus, systems and methods forthe detection and treatment of atrial fibrillation and relatedconditions Many embodiments provide a system including a pacemakercoupled to endocardial or epicardial leads having a distributed patternof bipolar electrode for the early detection and treatment of atrialfibrillation.

Referring now to FIGS. 1-2, an embodiment of a system 5 for thedetection and treatment of atrial fibrillation comprises a cardiac pacemaker or related device 10, and one or more leads 20 positionable in/onthe atria A and/or ventricles V of the heart H. Leads 20 can be coupledto pacemaker 10 by means of a mufti-lead connector 12. In variousembodiments, leads 20 can include: a lead 21 positionable on theendocardial wall ENW of the right atria RA for sensing and pacing theright atria; a lead 22 positionable on the epicardial wall EPW of theleft atria LA for sensing and pacing the left atria, a lead 23positionable on the endocardial wall of the right ventricle RV forsensing and pacing the right ventricle and a lead 24 positionable on theendocardial wall of the left ventricle LV for sensing and pacing theleft ventricle.

Referring now to FIGS. 3-6, in various embodiments, leads 21 and/or 22can comprise an apparatus 30 for the detection and treatment of atrialarrhythmia. Apparatus 30 can comprise a lead 40 having proximal anddistal portions 41 and 42 and a plurality of electrode assemblies 50coupled to the lead. As is described below, electrode assemblies 50 aredistributed in a pattern 63 along lead 40 so as to define an area 60 fordetecting and locating a foci of aberrant myoelectric activity causingatrial fibrillation. Apparatus 30 including lead(s) 40, can beconfigured for placement in various locations in the heart including theright atria RA, as is shown in the embodiment of FIG. 3, or the leftatria LA, as is shown in the embodiment of FIG. 4. FIG. 4 also shows anembodiment of device 30 having a plurality 40 p of leads 40 coupled inparallel to electrode assemblies 50 and pacemaker 10. In these andrelated embodiments leads 40 can be coupled to a common connector 14,which can be the same as connector 12.

The proximal portion of lead 40 includes an end 41 e configured to becoupled to a pacemaker 10 or a related device. The distal portion 42 ofthe lead is configured to be positioned in an atrial chamber (right orleft) AC of the heart H. Lead 40 comprises an outer sheath 43surrounding a plurality of conductive wires 44 each having an insulativesheath 45 over all or a portion of their lengths. Conducive wires 44 cancomprise copper or other conductive metal known in the art. Desirably,lead 40 also has sufficient flexibility and pushability as is known inthe catheter arts to be advanced into the atrial chamber of the heartfrom a percutaneous introductory site such as the jugular vein in theneck or other like site.

In many embodiments, electrode assembly 50 comprises a pair 51 ofbipolar electrodes 52 which are disposed in or otherwise positioned on apatch 53 or other support layer or structure 53 that can be attached tothe heart wall. Electrode assembly 50 and electrodes 52 are configuredto sense electrical activity within a region of myocardial tissue MTwithin the heart wall HW of the atria to detect an ectopic or other fociF of abnormal electric activity and send a pacing signal 56 to the heartwall to depolarize region MT containing the Foci F. Electrodes 52 aretypically circular and can have diameters in the range of 1 to 10 mmwith specific embodiment of 2, 5 and 7 mm, larger sizes are alsocontemplated. They can comprise various conductive metals known in theart including gold, platinum, silver, stainless steel and alloysthereof. They are desirably positioned on the tissue contacting surface55 of assembly 50, but also may be recessed within the interior of theassembly so as to be capacitively coupled to the heart wall.

In preferred embodiments, the electrodes 52 of electrode assembly 50 areconfigured as bipolar electrodes. Such embodiments allow the depth ofelectrical energy delivered to myocardial tissue for purposes of pacingand cardioversion to be precisely controlled. However in alternativeembodiments, electrodes 52 can be configured as monopolar electrodeswith current flowing to a return electrode (not shown) positioned atanother location on lead 40 or another lead 20.

Electrode assembly 50 can be attached to the heart wall HW throughseveral different means. According to an embodiment shown in FIG. 6 b,the patch can include one or more attachment elements 57 that havetissue penetrating anchoring portions 57 a which penetrate and anchorinto the heart wall HW. Suitable attachment elements 57 can includevarious helical coils or barbed needles as is shown in FIG. 6 b. Patch53 may also be attached to the heart wall through use of biocompatibleadhesives known in the art. In specific embodiments, the adhesive cancomprise thermally activated adhesives that are activated by heat fromflowing blood or electrical energy delivered from electrodes 52.

In various embodiments, lead 40 can include a plurality of electrodepairs 52/assemblies 50 which can be positioned in a distributedarrangement on the lead. In particular embodiments, the lead 40 caninclude between 2 to 10 pairs of electrodes with specific embodiments of3, 4, 5, 6, 7 and 8 electrode pairs. Greater and lesser numbers ofelectrode pairs also contemplated depending upon the size and shape ofatrial or ventricular chamber. The electrode pairs can be substantiallyequidistant from each with other spacing arrangements also contemplated.For example, particular spacing arrangements can be configured toaccount for the shape and size of a particular patient's atria which canbe determined by prior imaging of the patient's heart. In specificembodiments, the spacing between electrode pairs 52 can be in the rangefrom about 1 to about 5 cms with greater and lesser distances alsocontemplated.

Desirably, the spacing and number of electrodes pairs 52 on lead 40 orother lead are configured to allow the electrodes to sense theelectrical activity (e.g., the amount and time course of depolarization)of a selected area 60 of myocardial tissue MT within the atria orventricle. This in turn, allows for the generation of a conduction map61 of tissue area 60. Conduction map 60 can be used to detect for thepresence of one or more ectopic or other foci F of aberrant electricalactivity within area 60.

In various embodiments, electrode pairs 52 can be arranged in acircular, oval or other distributed pattern 62 around a selected area 60of the atrial or ventricular wall as is shown in the embodiments ofFIGS. 3 and 4. In particular embodiments, electrode pairs 52/assemblies50 are arranged in circular, oval or other pattern 62 around the SA nodeas is shown in the embodiment of FIG. 3 (desirably, the electrode pairs52 are positioned to be substantially equidistant from the SA node).Such embodiments allow for the detection of particular foci F causingpremature depolarization of the Atria by allowing comparison of theearliest depolarization within the entire area 60 (or adjacent to it) tothat of the SA node. As is described herein, software algorithmsresident 130 within pacemaker 10 can be used to detect the location LFof such foci F and then send a pacing signal to that location to takeconductive control of the Foci and prevent it from causing AF.

In addition to electrodes 52, lead 40 can also include other sensors 70for detection of various electrical and/or mechanical properties. Inparticular embodiments, sensors 70 can include an accelerometer 70, suchas a 3 axis accelerometer for detection of atrial or other heart wallmotion as is shown in the embodiment of FIG. 4. Similar to electrodes52, sensors 70 be arranged in selectable distributed pattern 62 on theendocardial or epicardial surface of the heart, such as a circular, ovalor other pattern.

Patch 53 will typically have an oval or other like shape, particularlyfor bipolar electrode embodiments, though other shapes are alsocontemplated. All or a portion of the patch can comprise variousbiocompatible polymers known in the art including PTFE, polyurethane,silicone and various other elastomers known in the. Desirably patch 53has sufficient flexibility to conform to shape of heart wall as well asbend and flex with the motion of the heart so as to remain attached tothe heart wall and not impede the motion of the heart wall. Patch 53 canalso include one or more biocompatible non-thrombogenic coatings 58 suchas silicone or other elastomeric coating. Coatings 58 can also have onemore drugs 58 d embedded in the coating, so as to be elutable over anextended period of time up to years. Drugs 58 d can include variouscompounds such as Taxol or compound known in the stent arts for reducingplatelet and cellular adhesion to the patch. Drugs 58 d can also includevarious antibiotics and antimicrobials such as vancomyacin, cefamandol,gentamicin and silver compounds for reducing the likelihood of bacterialadhesion and growth, or infection of patch 53. In some embodiments,patch 53 can have a multilayer construction, in these and relatedembodiments, coating 58 can comprise a layer 58 which will typically bea tissue contacting layer 58.

In various embodiments, all or a portion of patch 53 and/or electrodes52 can comprise a radio-opaque or echogenic material for visualizing alocation of assembly 50 and/or electrodes 52 in the heart underflouroscopy, ultrasound or other medical imaging modality. Suitableradio-opaque materials include platinum and titanium dioxide. Inparticular embodiments, patch 53 can include a marker section 59 madeout of such materials for visualizing the location of the electrode pair51. Desirably, marker 59 is centrally located on the patch so as to beequidistant from each electrode 52, to enable the physician to use themarker as a guide for placing the electrodes at a desired location onthe heart wall. Alternatively, marker 59 can be positioned on an edge ofpatch 53 as is shown in FIG. 6 a.

In use, markers 59 allow for the precise placement of the electrodeassemblies 50 along the endocardial wall of either the atria or theventricles so as to define the selectable area 60 of the heart formeasurement of electrical activity. For example, in particularembodiments the markers can be aligned with a superimposed image of analignment template that marks the desired location for each electrodeassembly. The markers also allow the physician to determine throughvarious cardiovascular imaging methods that the electrode assembliesremain attached to heart wall over time. Additionally, once an ectopicor other foci F of aberrant electrical activity has been detected, theycan be used as a point of reference for performing various RF ablativeprocedures to ablate the area of tissue responsible for the foci orotherwise create a conduction block around it.

Referring now to FIG. 7, pacemaker 10 can include various circuitry andother components. Some of the typical circuitry 110 and electronicdevices 120 in a pacemaker 10 or like device can include power controlcircuitry 111, amplification and sensing circuitry 112, pacing circuitry113, telemetry circuitry 114, micro-controller/micro-processor devices121 and memory devices 122. One or more software algorithms 130 can bestored in memory device 122 and/or processor 121 for implementation byprocessor 121. Such algorithms 130 can include cardiac mapping and focidetection algorithms, pacing algorithms (both atrial and ventricular),atrial fibrillation detection algorithms, ventricular fibrillationdetection algorithms, cardioversion algorithms (high and low voltage(e.g., 8 to 10 volts) and combinations thereof.

In embodiments of methods for positioning apparatus 30 in the body, thephysician can place the endocardial lead in the right atrium byadvancement from a percutaneous introductory site in the jugular vein ora related site. As described above, the desired positioning of theelectrode assemblies 50 in the atria can be achieved by imaging theheart during placement and observing the position of markers 59. Theepicardial leads can be placed using surgical techniques such as amini-thoracotomy or a minimally invasive procedure using endoscopy.Additional leads can be positioned as needed in the right or leftventricles using minimally invasive or surgical techniques. One or moreof these leads can be subsequently coupled to a pacemaker 10 positionedin the chest or other location.

In exemplary embodiments of methods for using the invention, system 5and atrially positioned leads 40 can be used to detect and treat atrialfibrillation in the following fashion. The distributed electrodeassemblies can be used to monitor the patient's EKG including the P waveas well as map conduction in the area within or adjacent thatcircumscribed by the electrode assemblies, preferably this area includesthe SA node. Atrial fibrillation can be detected based on theelimination or abnormality of the P wave as is shown in FIGS. 8 b and 8c. When AF occurs, using the conduction map, the location of the ectopicor other foci causing the atrial fibrillation can be identified bylooking at the time course of depolarization and identifying locationsthat depolarize before the SA node. Cardioversion can then be performedas described below to return the heart to normal sinus rhythm.

After cardioversion is performed and the heart returned to normal sinusrhythm, the electrode assemblies nearest that foci can then be used tosend a pacing signal to that site and surrounding tissue to prevent thesite from causing another episode of atrial fibrillation. Also, thelocation of that site can be stored in memory of the pacemaker so thatnext time abnormal atrial depolarization is detected, a pacing signalcan be sent immediately to that site to prevent the occurrence of AF. Insome embodiments, a site of early activation can be paced continuously.Atrial pacing can be performed to produce a stimulated P wave, P_(s)which can be triggered off the R wave, R, or the R to R interval, R_(i)as is shown in FIGS. 8 a and 8 b with appropriate time adjustment Ta forfiring during the time period Tp when the normal P wave would beexpected to occur.

In addition to detection of foci and other early activation/abnormalconductions sites in the atria, atrial fibrillation can also be detectedusing an accelerometer 71 such as a 3-axes accelerometer placed on theatrial wall (either epdicardial or endocardial) to sense atrial wallmotion as is shown in the embodiment of FIG. 4. Such motion ispredictive of atrial fibrillation via the effects atrial fibrillationhas on atrial wall motion which typically flutter as a result. Thesignal from the accelerometer can be used to supplement the electricalsignals from the bipolar leads positioned on the left atria to increasethe predictive power of various algorithms used by the pacemaker for thedetection of AF. Additionally, sensory inputs from the accelerometer canalso be used to assess the effectiveness of atrial pacing signal inpreventing AF and/or returning the heart to normal sinus rhythm.

As described above, when an episode of atrial fibrillation has beendetected embodiments of the invention can also be used for performingcardioversion to convert the atria from a fibrillative state back tonormal sinus rhythm. In these and related embodiments, the pacemaker cansimultaneously send a higher voltage pacing signal (in the range of 8 to10 volts) to all or majority of the pairs of distributed electrodes tosimultaneously depolarize (also described herein as conductivelycapture) a large enough area of the atrial myocardium to stop theaberrant currents causing the atrial fibrillation. These voltages, whilehigher than those used for pacing to prevent AF, are much lower thanthose typically used during conventional internal cardio version (in thehundreds of volts) or external cardioverions (in the thousands ofvolts). Such lower voltages can be used because the stimulation isdelivered by a multipoint source (resulting in higher current densities)and to a much smaller area of the heart than during typical internal orexternal cardioversion. By using voltages lower than those typicallyused during internal or external cardioversion, the pain experienced bythe patient can be greatly reduced. The other benefit of this approachis that by using bipolar electrodes at each site, the electrical energydelivered to the heart can be contained to a relatively small region sothat the risk of stimulating the ventricles (an unwanted effect in thiscase) is very small. The voltage level for achieving cardioversion canbe adjusted based on one or more of the following factors (the“conversion voltage adjustment factors”): i) the size of the area oftissue bounded by distributed electrode pairs (smaller areas requireless voltage); ii) the location of the ectopic foci (the closer the focito a particular electrode pair the less the required voltage; iii) thenumber of foci (larger number of foci may require larger voltages); iv)the number of electrode pairs defining the area (the more electrodes thelower the voltage); and v) the number of prior episodes of AF (a largernumber of episodes may require higher voltage). One or more of thesefactors can be programmed into the algorithm resident within thepacemaker which controls the cardioverion process. Also the conversionalgorithm can programmed to use the lowest possible voltage at first,and then progressively increase it until conversion is achieved. Thevoltage which achieves conversion can then be stored in memory and usedagain as a starting point in a subsequent conversion attempt with tuningor fine tuning using one or more of the five conversion voltageadjustment factors described above.

CONCLUSION

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to limit the invention to the precise forms disclosed. Manymodifications, variations and refinements will be apparent topractitioners skilled in the art. For example, embodiments of theapparatus for detection and treatment of atrial arrhythmias andfibrillation can also be adapted for detection and treatment of variousventricular arrhythmias.

Elements, characteristics, or acts from one embodiment can be readilyrecombined or substituted with one or more elements, characteristics oracts from other embodiments to form numerous additional embodimentswithin the scope of the invention. Moreover, elements that are shown ordescribed as being combined with other elements, can, in variousembodiments, exist as standalone elements. Hence, the scope of thepresent invention is not limited to the specifics of the describedembodiments, but is instead limited solely by the appended claims.

1. (canceled)
 2. A method for treating and/or preventing atrialfibrillation in a patient, the method comprising: providing an apparatuscomprising: an electrical lead having a proximal and distal portion, thedistal portion being positionable in an atrial chamber of the heart; theproximal portion having an end configured to be coupled to a pacemakerdevice; the lead having sufficient flexibility to be advanced into anatrial chamber of a heart from a percutaneous introductory site; and aplurality of pairs of bipolar electrodes, the electrode of each pairbeing (i) coupled to a conductive element of the lead, (ii) positionedon a membrane patch configured to be attached to a wall of the heart,and (iii) configured to at least sense an electrical signal of the wallof the heart; placing a plurality of membrane patches on the wall of theheart to position the plurality of pairs of bipolar electrodes in apattern to define a detection area for detecting aberrant electricalactivity in the heart; measuring electrical activity of the heart usingthe plurality of bipolar electrodes; and detecting aberrant electricalactivity in the heart causing the onset of atrial fibrillation (AF)using the measured electrical activity.
 3. The method of claim 2,wherein the plurality of membrane patches are positioned on anendocardial surface of the heart.
 4. The method of claim 2, wherein theplurality of pairs of bipolar electrodes comprises at least three pairsof bipolar electrodes.
 5. The method of claim 2, wherein the pluralityof pairs of bipolar are arranged in a substantially circular or ovalpattern.
 6. The method of claim 2, wherein the aberrant electricalactivity is detected by identifying a location in the detection areawhich depolarizes before the patient's SA node during an episode of AF.7. The method of claim 2, wherein the aberrant electrical activity isdetected by identifying a location in the detection area which has theearliest depolarization during an episode of AF.
 8. The method of claim2, wherein the aberrant electrical activity is detected by detecting anabnormal P wave in the patient's EKG.
 9. The method of claim 2, furthercomprising sending a pacing signal to a foci of the aberrant electricalactivity to prevent the aberrant electrical activity from causing AF.10. The method of claim 9, wherein the pacing signal is sentcontinuously.
 11. The method of claim 9, wherein the pacing signal issent using a pair or electrodes of the plurality that is nearest thefoci of aberrant electrical activity.
 12. The method of claim 9, whereinthe pacing signal is configured to produce a stimulated P wave.
 13. Themethod of claim 12, wherein the pacing signal is triggered of thepatient's R-wave or R to R interval.
 14. The method of claim 2, whereinthe aberrant electrical activity is detected by the absence orabnormality of a measured signal representative of the patient's P-wave.15. The method of claim 2, further comprising: sensing a wall motioncharacteristic of the atria using an accelerometer placed on the wall ofthe atrial; and using the sensed wall motion characteristic to detectthe occurrence or absence of AF.
 16. The method of claim 15, wherein theaccelerometer is placed on the epicardial wall of the atria.
 17. Themethod of claim 14, wherein the accelerometer is a 3D accelerometer. 18.The method of claim 15, wherein AF is detected using analysis of boththe sensed wall motion and the measured electrical activity.
 19. Themethod of claim 15, further comprising: sending a pacing signal to theaberrant electrical activity to prevent the site from causing AF,wherein the sensed wall motion characteristic is used to assess theeffectiveness of the pacing signal in preventing AF and/or returning theheart to normal sinus rhythm.
 20. A method for treating atrialfibrillation in a patient, the method comprising: providing an apparatuscomprising: an electrical lead having a proximal and distal portion, thedistal portion configured to be positioned in an atrial chamber of theheart; the proximal portion having an end configured to be coupled to apacemaker device; the lead having sufficient flexibility to be advancedinto an atrial chamber of a heart from a percutaneous introductory site;and a plurality of pairs of bipolar electrodes, the electrode of eachpair being (i) coupled to a conductive element of the lead, (ii)positioned on a membrane patch configured to be attached to a wall ofthe heart, and (iii) configured to at least sense an electrical signalof the wall of the heart; placing a plurality of membrane patches on thewall of the heart to position the plurality of pairs of bipolarelectrodes in a pattern to define a detection area for detectingaberrant electrical activity in the heart; measuring electrical activityof the heart using the plurality of bipolar electrodes; detectingaberrant electrical activity in the heart causing the onset of atrialfibrillation (AF) using the measured electrical activity; and upondetection of AF, sending a cardioversion signal to the atria using atleast a majority of the plurality of pairs of bipolar electrodes tosubstantially depolarize an area of the atrial myocardium, thedepolarized area sufficient in size to stop the aberrant signals causingthe AF.
 21. The method of claim 20, wherein the atria are converted froma fibrillative state to normal sinus rhythm.
 22. The method of claim 20,wherein the voltage of the cardioversion signal is in the range about 8to 10 volts.
 23. The method of claim 20, wherein the plurality membranepatches are positioned on an endocardial surface of the heart.
 24. Themethod of claim 20 further comprising: controlling the penetration depthof energy delivered from the plurality of electrode pairs to a selecteddepth of the atrial myocardium.
 25. The method of claim 24, wherein thepenetration depth is controlled so as to substantially reduce the riskof stimulating the patient's ventricles.
 26. The method of claim 20,further comprising: adjusting a voltage used for the cardioversionsignal.
 27. The method of claim 26, wherein the voltage is adjustedresponsive to a location of the aberrant electrical activity.
 28. Themethod of claim 26, wherein the voltage is adjusted responsive to thesize of the area bounded by the plurality of electrode pairs.
 29. Themethod of claim 26, wherein the voltage is adjusted responsive to thenumber of electrode pairs used to send the cardioversion signal.
 30. Themethod of claim 26, wherein the voltage is adjusted to a minimum levelfor converting the atria from a fibrillative state to normal sinusrhythm.
 31. The method of claim 26, wherein the voltage is adjustedresponsive to a number of prior occurrences of AF.
 32. The method ofclaim 25, wherein the voltage is adjusted responsive to a voltage usedfor cardioversion during a previous episode of AF.
 33. The method ofclaim 20, further comprising: determining if AF still persists bymeasuring the electrical activity of the heart with the plurality ofelectrode pairs; and sending a subsequent cardioversion signal to theatria.
 34. The method of claim 33, wherein the voltage of the subsequentcardioversion signal is adjusted upwards relative to the voltage of theprior cardioversion signal.